For example, in a process of manufacturing a 3D-NAND type nonvolatile semiconductor device, a laminated film including a plurality of silicon oxide films (SiO2 films) and a plurality of silicon nitride films (SiN films) alternately laminated is formed, a memory hole (channel hole) is formed in the laminating direction, a SiO2 film, a SiN film and a SiO2 film are sequentially formed in the memory hole by CVD, ALD or the like, a polysilicon film is formed, and then the center part of the memory hole is filled with a SiO2 film to form a channel part. Thereafter, a trench is formed in the laminating direction of the laminated film, the SiN film is removed by wet etching through the trench, a tungsten film to be a gate electrode is buried in a space generated after the removal of the SiN film via a TiN film, and the trench is filled with an SiO2 film or the like.
In recent years, as the design rule of semiconductor devices has been increasingly miniaturized, there is a need to form a thin and uniform SiO2 film on the surface of a laminated film of a SiO2 film and a SiN film in which a memory hole is formed, by CVD or ALD.
However, when the SiO2 film is formed on the surface of the laminated film of the SiO2 film and the SiN film by CVD or ALD, since the SiN film in the laminated film is more likely to diffuse oxygen than the SiO2 film to generate a grown oxide in the SiN film, the formed SiO2 film is thicker at the SiO2 film portion of the laminated film and is thinner at the SiN film portion, which makes it difficult to form a thin and uniform SiO2 film.